574 GLACIAL FOEMATIONS OF ERIE AND OHIO BASINS. 



reaching an altitude of over 800 feet, or about 50 feet above the bordering 

 marshy tracts and fully 60 feet above the St Marys River, while the greater 

 part stands 20 to 30 feet above the marshy tracts that border it. It is 

 traversed by sandy ridges, to which Dryer has given attention, and which 

 have received individual description in his report on Allen County, Ind.^ 

 The ridges are in some cases about a mile long and have a tendency to 

 trend east-northeast to west-southwest, but various other trends are assumed 

 by the different ridges. In some cases there is a main ridge from which 

 branches lead ofiF at nearly a right angle. The ridges are 10 to 30 feet in 

 height and vary in width from a few rods up to nearly one-fourth mile. 

 There are similar ridges on the crest of the moraine in the east part of Fort 

 Wayne. The most prominent one is estimated by Dryer to have had a 

 height of 30 feet previous to its removal by the railroad. The portion 

 remaining (east of the freight yards) stands about 15 feet above the 

 bordering portion of the moraine. This ridge has an east-west trend, 

 parallel with the lake outlet and at a right angle to the crest of the moraine. 

 It was originally a mile or more in length (Dryer), but the greater part 

 is now removed. Similar ridges also occur in the west part of Fort Wayne 

 on the east bluff of the St. Marys River. They follow the bluff in a curving 

 course from southwest to northeast. These ridges seem to be due in large 

 part to the work of wind upon sand that was deposited in the outlet. This 

 interpretation, it will be noted, differs from that given by Dryer in the report 

 above cited, it being his opinion that they are of glacial origin. 



The portion of this moraine north of the outlet, as noted by Gilbert, 

 is less strongly in contrast with the adjacent plain from Fort Wayne north- 

 eastward than in the portion bordering the St. Marys River, though its 

 surface is "gently rolling."^ It presents but little variation from Fort 

 Wayne northeastward across northwestern Ohio into Michigan. 



THICKNESS AND STRUCTURE OF THE DRIFT. 



From the eastern end in Ohio westward to Decatur, Tnd., the general 

 thickness of the drift (not including that in buried valleys), is scarcely 

 twice as great as the relief of the moraine, there being numerous outcrops 

 of rock along the shallow valleys that follow the outer border of the 

 moraine, while the wells along the moraine and on the border plain often 



1 Sixteenth Ann. Rept. Geol. Sm-vey Indiana, 1889, pp. 116-118. '^ Geology of Ohio, Vol. 1, 1873, p. 541. 



